It is not possible to prevent lubricant losses to the environment. Ecological balance is of great concern or survival of living beings. Industrial experts estimate that 70% to 80% of lube oil leaves the system through leaks, spills, line breakage and fitting failure. No doubt, petroleum based lubricants increase the capacity and speed of industry and other machines. It however, leads to increase the toxicity of the environment. It is affecting living organisms including plants, animals and marine life for many years. The petroleum based lubricating oils are hydrocarbons consisting of naphthenes, paraffins, aromatics, polynuclear aromatics and unsaturates. Petroleum based lube-oils, generally suffer from many disadvantages such as high toxicity to the environment, poor biodegradability and inconsistent characteristics with change in crude oil composition. The other types of lubricants known as synthetic lubricants are designed for use in extreme conditions of temperature, pressure, radiation or chemical and have excellent lubricity and thermal stability. The synthetic lubricants are relatively costly, may also be toxic to environment.
Gears transmitted rotary motion. Modern metallurgy has greatly increased the useful life of industrial and automotive gears. Gear oils are used to protect the gears and reduce the friction. Gear oils are classified by the American Petroleum Institute using GL ratings, e.g. GL4 or GL5 oil. API viscosity ratings for latest gear oils are 75W90; or 10W40 or multigrade. Great efforts have been made during the last 25 years by several countries and major industries to develop and find more and more environment friendly—nontoxic products and technologies which have a less negative impact on environment. So, the past development of gear oils may be summarized as:                The use of stable mineral base oil for required performance.        The use of paraffinic mineral base oil to reduce toxicity.        Use of synthetic base oil such as silicone oil, sulfurized oil, polymers, polybutenes, dibasic acid esters, fluoropolymers, polyol esters, phosphate esters, poly-alpha olefins, etc. to reduce toxicity and enhance lubricant life. Fully synthetic gear oils have a greater resistance to shear breakdown than mineral oils but they are not economical.        Development of more efficient gear oil additives for better performance.        Use of biodegradable polyol—fatty acid—esters and mineral oil/synthetic oil blend to increase eco-friendliness.        
So, fully biodegradable gear oil from renewable source (vegetable oil) is not developed. In the eco-sensitive area application of biodegradable lube oil is required. Till now most of eco-friendly type gear oils are either biodegradable/non-toxic with poor performance or they have good performance but lack the desired eco-friendliness. Thus, there is a need for a gear oil composition that has both high performances and complete biodegradability.
Certain types of mono-esters from non-edible vegetable oils are useful to reduce pollution, completely biodegradable; these are compatible to mineral oil, and capable of providing the desirable lubricant properties such as good boundary lubrication, high viscosity index, high flash point and low volatility but show poor oxidation stability. Low thermo-oxidative stability of vegetable oils can be improved by suitable chemical modification and additives. Converting vegetable oils (tri-ester) into mono-ester to gain stability is well known chemical modification. The stability can be further improved by partial hydrogenation, epoxidization or alkylation with aromatics.
Vegetable oil that is long chain fatty acid triester of glycerol possesses most of the desirable lubricant properties such as high viscosity index, high flash point, low volatility and good boundary lubrication. As per fatty acid typical composition of vegetable oils, it contains unsaturated acids such as oleic C 18:1 as a major component. It is understood that some of the carbon chain lengths of the carboxylic acids and/or esters discussed here by average carbon numbers. This reflects the fact that some of the carboxylic acids and/or esters are derived from naturally occurring materials and therefore contain a mixture of compounds the major component of which is the stated compound. Non-edible vegetable oil, which are found in abundance in India are, (1) Neem—Mellia Azadirachta in the family Meliaceae, (2) Karanja—Pongamia glabra in the family Leguminaceae, (3) Ricebran—Oryza sativa in the family Graminaceae, (4) Mahua—Madhuca Indica & Madhuca Longifolia, (5) Castor—Ricinus communis in the family Euphorbiaceae (spurge), (6) Linseed—Flax oil plant Linium usitatissimum (Linacae), (7) Other similar vegetable oil or their mixture.
Extensive works were done in the field of development of biodegradable lube base stock and load bearing additive at Indian Institute of Petroleum (CSIR). Several patent applications were filed. The present work is in the continuation of “Biodegradable Lubricants” speciality product from non-edible vegetable oils”. Patent applications are:                A process for the preparation of Phospho sulfurized derivatives or hydrogenated cardanol useful as antiwear, antifriction extreme pressure additives; O. N. Anand, et. al. IPA (Indian Patent Application) 2522/DEL/98 Dated 28 Aug. 1998, now Indian Patent No. 215707. Assignee—IIP/CSIR        A formulation useful as an extreme pressure antiwear & antifriction additive for industrial gear oils; O. N. Anand, et. al. IPA 2521/DEL/98 Dated 26 Aug. 1998, now Indian Patent No. 215826. Assignee—IIP/CSIR        A Process for the Prep. of ecofriendly Lubricants from vegetable oils, O N Anand, et. al; IPA 363/DEL/2004; 5 Mar. 2004, pending; Assignee—IIP/CSIR        Biodegradable lube for two stroke Gasoline Engine—A. K. Singh, et. al.,—IPA 779/DEL/2006, pending. Assignee—IIP/CSIR        Biodegradable hydraulic fluid—A. K. Singh, et. al. IPA 785/DEL/2006, pending. Assignee—IIP/CSIR        
A method for preparing the highly stable mono ester from vegetable oil was developed during the above works. Typical method is: the vegetable oil was dissolved in solvent and kept at low temperature. Filtered to remove gummy material and solvent was distilled off to get de-gummed oil. This oil is partially hydrogenated in a high pressure reactor having hydrogen and Raney Nickel as catalyst until low Iodine value was obtained. Then, primary alcohol C7-C12, partially hydrogenated vegetable oil and catalyst were added in a reactor for esterification. The reaction mixture was refluxed. The catalyst and glycerol were removed. Excess alcohol was removed by distillation under vacuum. Partially hydrogenated mono-ester is treated with per acid. Per acid is added drop wise to ester between 20-30° C. The addition is completed in 10-20 hours. The product is extracted by ether and washed repeatedly with water to remove acid and ether was distilled-off. The remaining ester is washed with hot water to pH 5-7. Partially hydrogenated epoxidized mono-ester was alkylated with alkyl aromatics under Friedel Kraft's reaction conditions. References may be made to:                O N Anand & M Pal, IIP Report, ‘Development of Ecofriendly Biodegradable Lubricants/Base stock’, August, 2002.        H. Wagner, R. Luther & T. Mang, Lubricant base fluids based on renewable raw materials: their catalytic manufacture and modification, Applied Catalysis A::General 221(2001)429-442.        S. Z. Erhan & S. Asadauskas, Lubricant base stock from vegetable oils, Ind. Crops and products, 11 (2000)277-282.        U. Schuchardt, R. Sercheli & R. M. Vargas, Transesterification of vegetable oils: a review, J. Braz. Chem. Soc., vol 9, no 1, 199-210, 1998.        
Reference may be made to U.S. Pat. No. 6,872,693 dated Mar. 29, 2005 by Cain, Assignee; The Lubrizol Corporation (Wickliffe, Ohio)—Mineral gear oils and transmission fluids. This invention relates to mineral oil based gear oils and transmission fluids which comprise a major amount of a mineral oil having an iodine number of less than 9 and where at least 55% of the saturates are aliphatic, and gear oil or transmission fluid additives. In one embodiment, the invention relates to a gear oil or transmission fluid composition comprising a major amount of lubricant basestock and at least one functional additive wherein a major amount of the lubricant basestock comprises a mineral oil having an iodine number of less than 9 and comprising at least 45% by weight of aliphatic saturates. These gear oils and transmission fluids have good viscosity and oxidation properties (Here, mineral oil are used non-biodegradable and non-renewable).
Reference may be made to U.S. Pat. No. 4,082,680 Dated Apr. 4, 1978 by Mitacek; Bill, assignee Phillips Petroleum Company (Bartlesville, Okla.)—Gear oil Composition. Shear-stable, high viscosity index gear oil formulations are formed by the inclusion into such formulations of a small amount of a hydrogenated butadiene-styrene copolymer having a butadiene content of 30 to 44 weight percent and a weight average molecular weight in the range of about 12,000 to about 20,000. (Here, blend of mineral oil and polybutadine are used, non-biodegradable and non-renewable).
Reference may be made to U.S. Pat. No. 4,164,475 dated August 14, 19 by Schieman; Richard D, assignee: The Standard Oil Company (Cleveland, Ohio)—Multi-grade 80W-140 gear oil. A multi-grade 80W-140 gear oil is described which is composed of certain mineral-oil stocks, a wear additive, a V.I. improver, a dispersant polymer and optionally a seal-swell agent 1. In a multi-grade gear oil composition comprising a major proportion of mineral lubricating oil, 5-6 volume percent sulfur- and phosphorous-containing wear additive, 16.6-18.6 volume percent V.I. improver, and 0-2.7 volume percent seal-swell agent, the improvement comprising using as the oil a petroleum-oil stock composed of 20-23 volume percent of a 5.0 centistokes at 210.degree. F. oil, 24-25 volume percent 14.0 centistokes at 210.degree. F. oil, and 26-30 volume percent 25.0 centistokes at 210.degree. F. oil, and from 0.1 to 1.5 volume percent of a dispersant polymer which is an alkyl methacrylate copolymer which has been grafted with a dialkyl amino methacrylate monomer. (Here, mineral oil is used, non-biodegradable and non-renewable).
Reference may be made to U.S. Pat. No. 5,358,650 dated Oct. 25, 1994 Srinivasan; Sanjay and Hartley; Rolfe J. Assignee: Ethyl Corporation (Richmond, Va.) Gear oil compositions. A “cold-clash” gear problem associated with vehicular manual transmissions exposed to the cold is overcome by use of a special all-synthetic gear oil composition. The composition is composed of base oil and specified additive components. The base oil is a blend of di-(2-ethylhexyl)sebacate and three hydrogenated poly-.alpha.-olefin oligomers having kinematic viscosities at 100.degree. C. of about 40, about 8 cst and about 2 cst in specified proportions. The additive components comprise an organic sulfur-containing antiwear and/or extreme pressure agent, an organic phosphorus-containing antiwear and/or extreme pressure agent, a copper corrosion inhibitor, a rust inhibitor, a foam inhibitor, and an ashless dispersant. The gear oil has a boron content of about 0.0025 to about 0.07 wt %. (Here, blend of sebacate and PAO synthetic oil are used, less-biodegradable, a portion is non-renewable, higher cost).
Reference may be made to U.S. Pat. No. 5,571,445 dated Nov. 5, 1996; by Srinivasan, et al. Assignee: Ethyl Corporation (Richmond, Va.)—Gear oil compositions, A “cold-clash” gear problem associated with vehicular manual transmissions exposed to the cold is overcome by use of a special all-synthetic gear oil composition. The composition is composed of base oil and specified additive components. The base oil is a blend of dialkyl ester of an aliphatic dicarboxylic acid having a maximum pour point of about −55.degree. C. and a maximum kinematic viscosity at 100.degree. C. of about 4 cst, and three hydrogenated poly-.alpha.-olefin oligomers having kinematic viscosities at 100.degree. C. of about 40, about 4-8 cst and about 2 cst in specified proportions. The additive components comprise an organic sulfur-containing antiwear and/or extreme pressure agent, an organic phosphorus-containing antiwear and/or extreme pressure agent, a copper corrosion inhibitor, a rust inhibitor, a foam inhibitor, and an ashless dispersant. The gear oil has a boron content of about 0.0025 to about 0.07 wt % (here blend of dialkyl ester and PAO base stocks were used, less-biodegradable, a portion is non-renewable, higher cost.)
Reference may be made to U.S. Pat. No. 5,364,994 dated Nov. 15, 1994 by Scharf; Curtis R, Assignee: The Lubrizol Corporation (Wickliffe, Ohio)—Lubricating compositions containing .alpha.-olefin polymers. The invention deals with viscosity improvers which are .alpha.-olefin polymers and are particularly useful in lubricating compositions comprising (A) a liquid .alpha.-olefin polymer having a number average molecular weight from about 2,000 to about 100,000 and having derived from .alpha.-olefins having from about 4 to about 30 carbon atoms, provided further that (A) has a bimodal molecular weight distribution having (i) a peak molecular weight maximum at 2,000 to 5,000 for a lower molecular weight component and (ii) a peak molecular weight maximum at 50,000 to 75,000 for a higher molecular weight component; (B) an oil of lubricating viscosity land (C) at least one member selected from the group consisting of a friction modifier, a sulfurized olefin, an ash-producing detergent and, an ashless dispersant. (Here, synthetic oil is used, less-biodegradable, higher cost and a portion is non-renewable).
Reference may be made to U.S. Pat. No. 5,942,470 dated Aug. 24, 1999 by Norman, et al. Assignee: Ethyl Petroleum Additives, Inc. (Richmond, Va.)—Lubricant compositions. Gear oils and gear oil additive concentrates of enhanced positraction performance are described. They comprise: (i) at least one oil-soluble sulfur-containing extreme pressure or antiwear agent; (ii) at least one oil-soluble amine salt of a partial ester of an acid of phosphorus; and (iii) at least one oil-soluble succinimide where R.sub.1 is an alkyl or alkenyl group having an average of 8 to 50 carbon atoms, and each of R.sub.2, R.sub.3 and R.sub.4 is a hydrogen atom or an alkyl or alkenyl group having an average of up to about 4 carbon atoms. These compositions preferably contain one, more preferably two, and most preferably all three of the following additional components: (iv) at least one amine salt of a carboxylic acid; (v) at least one nitrogen-containing ashless dispersant; and (vi) at least one trihydrocarbyl ester of a pentavalent acid of phosphorus (Here, synthetic oil are used less-biodegradable, higher cost and a portion is non-renewable).
Reference may be made to U.S. Pat. No. 6,649,574 dated Nov. 18, 2003 by Cardis, et al. Assignee: ExxonMobil Research and Engineering Company (Annandale, N.J.)—Biodegradable non-toxic gear oil A biodegradable lubricating oil composition especially useful as a gear oil employs a synthetic alcohol ester base-stock formed from mono- and dipentaerythritol with certain mono- and dicarboxylic acids or dicarboxylic acid anhydrides and an effective amount of a polyoxyalkylene alcohol demulsifying agent, a combination of alkylated organic acid and ashless succinimide rust inhibitors and an ashless dithiocarbamate antiwear and extreme pressure agent (Here, synthetic oil are used having higher cost).
In the prior art for producing gear oils, generally, mineral oils or blend of mineral oil with synthetic fluids or complex ester of fatty acids were used. The focus has been on the use of such simple mono-ester of non-edible vegetable oil for gear oil, which enhances the performance and biodegradability.
In view of the growing concern about the environment, there is a need for biodegradable gear oils, which are derived from renewable resources, reduce pollution, readily miscible with mineral oil and synthetics. These objectives must be met, while (simultaneously satisfying stringent performance standards.